Automatically Insert Into Post when uploading Media

That’s the pre-3.5 media interface so I think you must be on 3.4.x? Anyway the first way should work as long as you’re using the browser (non-multifile) upload… try changing

add_filter( 'flash_uploader', '_force_html_uploader' );

to

add_action( 'pre-html-upload-ui', '_force_html_uploader' );

and the “js/upload.js” (note the subdirectory – it’s expected to be in a “js” subdirectory of your theme directory) to

jQuery(document).ready(function(){
    if (typeof 'switchUploader' === 'function') switchUploader(1);
    if(jQuery(".savesend input")){
        jQuery(".savesend input").click();
    }
});

Neither change is that important, they just ensure your using the browser upload – which is important. The (other) important thing is that “js/upload.js” gets loaded (you can check it’s being loaded by inspecting the frame source).